In Long Term Evolution (LTE), in order to achieve a further increase in a system capacity, a further increase in a data transmission rate, and further reduction of latency in a radio section, a study of a radio communication scheme called 5G has been progressed. In 5G, various element techniques have been studied in order to satisfy requirements that latency in a radio section be less than or equal to 1 ms while achieving throughput of greater than or equal to 10 Gbps.
In 5G, a higher frequency band than that of LTE is assumed to be used. Here, since a propagation loss increases in a high frequency band, the application of massive Multi Input Multi Output (MIMO) in which beam forming with a narrow beam width is performed has been studied to compensate for it. Massive MIMO is a large-scale MIMO in which a plurality of antenna elements (for example, 100 elements) is installed at a base station side, and it is possible to reduce interference between mobile stations since it is possible to concentrate an electric field strength in a narrow region.
FIG. 1A illustrates an example of beam forming performed by a base station according to a related art such as LTE, and FIG. 1B illustrates an example of beam forming performed by a base station using massive MIMO. As illustrated in FIG. 1B, it is possible to transmit radio signals far away through beam forming with a narrow beam width.
FIG. 2A illustrates an operation example when a base station of related art performs multi-user MIMO (MU-MIMO), and FIG. 2B illustrates an operation example when a base station using massive MIMO performs MU-MIMO. As illustrated in FIG. 2B, since the base station using massive MIMO has a sufficient degree of freedom of an antenna, it is possible to control interference highly by directing a thin beam to a desired mobile station and directing null (a direction in which a signal is not transmitted) to the other mobile station.